Sporotrichosis

Published on 18/03/2015 by admin

Filed under Dermatology

Last modified 18/03/2015

Print this page

rate 1 star rate 2 star rate 3 star rate 4 star rate 5 star
Your rating: none, Average: 0 (0 votes)

This article have been viewed 1653 times

Sporotrichosis

Mahreen Ameen and Wanda Sonia Robles

Evidence Levels:  A Double-blind study  B Clinical trial ≥ 20 subjects  C Clinical trial < 20 subjects  D Series ≥ 5 subjects  E Anecdotal case reports

image

Sporotrichosis is a deep, cutaneous fungal infection caused by Sporothrix schenckii, a rapidly growing dimorphic saprophytic fungus found in soil and plant matter, occurring worldwide, but more commonly in the tropics. Disseminated and internal infection is a risk in the immunocompromised and in advanced HIV infection. Cutaneous lesions develop following traumatic inoculation of S. schenckii. It is more common in some occupations such as horticulturists, carpenters, and miners due to inoculation with infected soil or wood. The initial lesion appears at the site of injury as an erythematous, ulcerated, or verrucous nodule. Lesions can be localized and are known as fixed-type sporotrichosis. The more common presentation is the lymphocutaneous form, where there is nodular lymphangitic spread.

Management strategy

Although there have been cases describing the spontaneous remission of sporotrichosis, it is common practice to treat the infection. Treatment includes local measures (thermotherapy), saturated solution of potassium iodide (SSKI), azoles, terbinafine and amphotericin B. Historically, uncomplicated lymphangitic and fixed forms of sporotrichosis have been treated with high dose SSKI initiated with five drops three times daily and increased as tolerated to 10 to 50 drops three times daily (equivalent to 250 mg to 1 g three times daily). Treatment is continued for 3 to 4 weeks after clinical cure. The mechanism of action of potassium iodide is not known but it is highly effective, with reported cure rates ranging from 80% to 100%. It is also inexpensive, and is first-line treatment for sporotrichosis in most developing countries. However, it is inconvenient to administer and side effects are common although not serious and include metallic taste, nausea, abdominal pain, and salivary gland enlargement.

Itraconazole is first-line therapy in countries where it is affordable, starting at a loading dose of 200 mg three times daily for 3 days followed by 100–400 mg daily. Cure rates for cutaneous and lymphocutaneous infection are high, generally 90–100%. Terbinafine (250–1000 mg daily) produces similar efficacy. Fluconazole (400–800 mg daily) therapy gives response rates of 63–71% and therefore is recommended for second-line therapy only. Ketoconazole is ineffective for the treatment of sporotrichosis.

There are no clinical trials to guide therapy for disseminated or meningeal sporotrichosis which can occur with immunosuppression. On the basis of case reports parenteral amphotericin B (AmB) is the preferred treatment (AmB deoxycholate 0.7 mg/kg daily, or as a lipid formulation 3.0–5.0 mg/kg daily). A lipid formulation of AmB is recommended for meningeal infection. Following AmB induction therapy, iItraconazole (200 mg twice daily) is given as maintenance therapy. Thermotherapy (using infrared and far infrared wavelengths to heat tissues to 42–43°C) is known to be effective although there are few reports of its use. It has a useful role in those for whom systemic therapies are contraindicated. There is limited clinical data demonstrating the potential of cryotherapy as an adjuvant to systemic therapy.

Specific investigations

The fungus is sometimes visualized with periodic acid–Schiff staining and is associated with extracellular sporothrix asteroid bodies, consisting of yeast surrounded by radiating eosinophilic spicules. Culture is the most sensitive means of diagnosis, and is characteristically rapid, with growth usually seen within 3 to 5 days. Infected material is inoculated onto Sabouraud’s dextrose agar at 25°C. The colonies are initially white or creamy with a wrinkled surface, which becomes progressively darker to a brown or black color. The diagnosis is confirmed by demonstrating dimorphism, or conversion to the yeast phase, achieved by incubation at 37°C on brain–heart infusion agar, which produces oval or cigar-shaped yeasts. Polymerase chain reaction is able to detect the fungus even in lesions with few organisms.